Influence of astaxanthin, zeaxanthin and lutein on DNA damage and repair in UVA-irradiated cells

In order to gain more knowledge about the antioxidant role of the predominant carotenoids (lutein and zeaxanthin) of the human retina, this study investigated their antioxidant activity and capacity. Astaxanthin was also studied, because its structure is very close to that of lutein and zeaxanthin. The antioxidant activity of these molecules was evaluated using chemiluminescence techniques, with lucigenin and luminol as chemiluminogenic probes for the superoxide radical and hydrogen peroxide, respectively. It was found that all three carotenoids have similar superoxide-scavenging activity. The effect on the reduction of H(2)O(2)-luminol chemiluminescence was present in the following order, zeaxanthin>astaxanthinlutein. Possible antioxidant capacity of these three compounds was sought using a biological system consisting of SK.N.SH human neuroblastoma and rat trachea epithelial cells subjected to oxidative stress from exposure to UVA radiation. In particular, we determined whether these compounds were capable of minimizing DNA damage and influencing the kinetics of DNA repair. DNA damage was assessed using the Comet assay, a rapid and sensitive single-cell gel electrophoresis technique used to detect primary DNA damage in individual cells. Neuroblastoma cells appeared more resistant to oxidative irradiation insult. The presence of carotenoids reduced DNA damage when rat epithelial cells were exposed to UVA radiation for 2min. A different result was obtained in experiments performed on neuroblastoma cells; in this case, the presence of carotenoid during UVA exposition increased the damage. The addition of carotenoids to epithelial cells after 2min of UVA exposition did not seem to improve the kinetics of DNA repair; on the contrary, zeaxanthin (after 60' incubation) and lutein (after 180' incubation) showed a genotoxic effect. The addition of carotenoids to neuroblastoma cells after 30' UVA exposition positively influences the kinetics of DNA repair in the first 15min of incubation. At longer exposition times, while the behaviour measured was not constant, a genotoxic effect was not observed. The data from this study provide additional information on the antioxidant and pro-oxidant activities of the predominant macular pigment carotenoids of the human retina.     

Organic-organic epitaxy of incommensurate systems: quaterthiophene on potassium hydrogen phthalate single crystals

Hot-wall epitaxy and molecular-beam epitaxy have been employed for growing quaterthiophene thin films on the (010) cleavage face of potassium hydrogen phthalate, and the results are compared in terms of film properties and growth mode. Even if there is no geometrical match between substrate and overlayer lattices, these films are epitaxially oriented. To investigate the physical rationale for this strong orientation effect, optical microscopy, atomic force microscopy, and X-ray diffraction are employed. A clear correlation between the morphology of the thin films and the crystallographic orientation is found. The results are also validated by surface potential calculations, which demonstrate the primary role played by the corrugation of the substrate surface.     

Grazing‐incidence X‐ray diffraction study of rubrene epitaxial thin films

The growth of organic semiconductors as thin films with good and controlled electrical performances is nowadays one of the main tasks in the field of organic semiconductor‐based electronic devices. In particular it is often required to grow highly crystalline and precisely oriented thin films. Here, thanks to grazing‐incidence X‐ray diffraction measurements carried out at the ELETTRA synchrotron facility, it is shown that rubrene thin films deposited by organic molecular beam epitaxy on the surface of tetracene single crystals have the structure of the known orthorhombic polymorph, with the (2 0 0) plane parallel to the substrate surface. Moreover, the exact epitaxial relationship between the film and the substrate crystalline structures is determined, demonstrating the presence of a unique in‐plane orientation of the overlayer.     

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast,Preliminary Authentication of Gemstones

The identification of gemstones is an important topic in the field of cultural heritage, given their enormous value. Particularly, the most important precious stones, namely diamond, emerald, ruby and sapphire, are frequently subjected to counterfeit by substitution with objects of lesser value with similar appearance, colour or shape. While a gemmologist is able to recognise a counterfeit in most instances, more generally, it is not easy to do this without resorting to instrumental methods. In this work, the use of UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) is proposed as a fast and easy method for the preliminary identification of gemstones, alternative to the classical methods used by gemmologists or to Raman spectroscopy, which is by far the instrumental method with the best diagnostic potential, but it cannot be used in situations of problematic geometric hindrance. The possibilities and the limitations given by the FORS technique are critically discussed together with the spectral features of the most important gemstones. Finally, the application of chemometric pattern recognition methods is described for the treatment of large sets of spectral data deriving from gemstones identification.     

Synthesis,Chiral Resolution and Enantiomers Absolute Configuration of 4-Nitropropranolol and 7-Nitropropranolol

We recently identified 6-nitrodopamine and other nitro-catecholamines (6-nitrodopa, 6-nitroadrenaline), indicating that the endothelium has the ability to nitrate the classical catecholamines (dopamine, noradrenaline, and adrenaline). In order to investigate whether drugs could be subject to the same nitration process, we synthesized 4-nitro- and 7-nitropropranolol as probes to evaluate the possible nitration of the propranolol by the endothelium. The separation of the enantiomers in very high yields and excellent enantiopurity was achieved by chiral HPLC. Finally, we used Riguera’s method to determine the absolute configuration of the enantiomers, through double derivatization with MPA and NMR studies.